In The Breakfast Club, John Bender is crawling through the ceiling space back to the library after being locked in the closet. He is reciting a joke to himself.

It goes:

Naked blonde walks into a bar with a poodle under one arm and a two-foot salami under the other. She lays the poodle on the table. The bartender says, "I suppose you won't be needing a drink." Naked lady says...

Then he falls through the ceiling. Any ideas of what the punchline ought to be?

The joke that Bender tells but never finishes (while crawling through the ceiling) actually has no punchline. According to Judd Nelson, he ad-libbed the line. Originally, he was supposed to tell a joke that would end when he came back into the library and said, "Forgot my pencil", but no one could come up with a joke for that punchline.

But I suppose if an appropriate punch line can't be thought of here, it can't be thought of anywhere!